1. Field of the Invention
The present invention relates to an electronic component, and more specifically, relates to an electronic component including a directional coupler.
2. Description of the Related Art
As an existing electronic component, for example, a coupler disclosed in Japanese Unexamined Patent Application Publication No. 2005-12559 is known. Hereinafter, the coupler disclosed in Japanese Unexamined Patent Application Publication No. 2005-12559 will be described with reference to the drawing. FIG. 3 is a perspective view of a coupler 500 disclosed in Japanese Unexamined Patent Application Publication No. 2005-12559.
The coupler 500 includes a dielectric substrate 502, a first conductor line 504, a second conductor line 506, via-hole conductors B1 to B4, first to fourth terminals 508-514.
The dielectric substrate 502 is composed of a plurality of substantially rectangular dielectric layers laminated to each other. The first conductor line 504 and the second conductor line 506 are line-shaped conductors provided on the dielectric layers, and are electromagnetically coupled to each other. The first terminal 508 and the fourth terminal 514 are external electrodes provided on the bottom surface of the dielectric substrate 502. The via-hole conductors B1 to B4 extend through the dielectric layers in the lamination direction. The via-hole conductors B1 and B2 connect both ends of the first conductor line 504 to the first terminal 508 and a second terminal 510, respectively. The via-hole conductors B3 and B4 connect both ends of the second conductor line 506 to a third terminal 512 and the fourth terminal 514, respectively.
In the coupler 500 disclosed in Japanese Unexamined Patent Application Publication No. 2005-12559, the element can be reduced in size as described below. In a general coupler, a first terminal and a fourth terminal are provided on side surfaces of a dielectric substrate. In this case, drawing conductors for electrically connecting both ends of a first conductor line to the first terminal and a second terminal, and drawing conductors for electrically connecting both ends of a second conductor line to a third terminal and the fourth terminal are needed. The drawing conductors extend from the both ends of the first conductor line and the both ends of the second conductor line toward the outer edges of dielectric layers. Thus, in order to ensure, on the dielectric layers, regions for providing the drawing conductors, the dielectric layers need to be increased in size. As a result, the coupler is increased in size.
Meanwhile, in the coupler 500 disclosed in Japanese Unexamined Patent Application Publication No. 2005-12559, both ends of the first conductor line 504 are connected to the first terminal 508 and the second terminal 510 through the via-hole conductors B1 and B2. Similarly, both ends of the second conductor line 506 are connected to the third terminal 512 and the fourth terminal 514 through the via-hole conductors B3 and B4. The via-hole conductors B1 to B4 extend in the lamination direction. Thus, in the coupler 500, regions for providing the via-hole conductors B1 to B4 do not need to be ensured on the dielectric layers. As a result, in the coupler 500 disclosed in Japanese Unexamined Patent Application Publication No. 2005-12559, the element can be reduced in size.
However, in the coupler 500 disclosed in Japanese Unexamined Patent Application Publication No. 2005-12559, warpage occurs in the dielectric substrate 502 as described below. More specifically, when firing the dielectric substrate 502, the dielectric layers, the first terminal 508, and the fourth terminal 514 contract in different contraction ratios. In addition, the first terminal 508 and the fourth terminal 514 are provided on the bottom surface of the dielectric substrate 502, and no terminal is provided on the top surface of the dielectric substrate 502. Since the first terminal 508 and the fourth terminal 514 are provided only on the bottom surface of the dielectric substrate 502, the dielectric substrate 502 has different contraction ratios in the top surface and the bottom surface. As a result, warpage occurs in the dielectric substrate